apps/tools: Make hello_rust_cargo buildable with make

[toku-mac]

Summary

Fix the Make-based build for Rust-enabled sim:nsh configurations.

This change addresses two Make/Cargo issues:

Add the missing Apple Silicon macOS Rust target mapping

When building sim:nsh with Make on an ARM64 macOS host, LLVM_ARCHTYPE is set to aarch64. However, apps/tools/Rust.mk did not handle aarch64 in RUST_TARGET_TRIPLE, so Cargo was invoked with an empty --target argument:

error: "--target" takes a target architecture as an argument.

The Make build now maps this case to the same target used by the CMake Rust helper: aarch64-apple-darwin

Pass -Zjson-target-spec to Cargo

The Rust build uses JSON target specifications for NuttX targets such as the simulator targets under apps/tools/. Cargo requires -Zjson-target-spec when building with these JSON target files.

Impact

• Impact on build: Enables building with Make/Cargo configurations.

Testing

I confirm that changes are verified on local setup and works as intended:

• Build Host(s): OS (macOS 26.5), CPU(Apple M1), compiler(Apple clang version 21.0.0)
• Target(s): arch(sim)
• Ensure your PATH environment variable is properly configured to allow execution of: menuconfig, olddefconfig, savedefconfig, and setconfig.
• Use the Rust toolchain version prior to nightly-2026-04-29 to avoid errors related to lib/rustlib/src/rust/library/std/src/sys/net/connection/socket/unix.rs.

Configuration:

make distclean
./tools/configure.sh sim:nsh
make menuconfig

printf "CONFIG_SYSTEM_TIME64=y
CONFIG_FS_LARGEFILE=y
CONFIG_TLS_NELEM=16
CONFIG_DEV_URANDOM=y
CONFIG_EXAMPLES_HELLO_RUST_CARGO=y
CONFIG_EXAMPLES_HELLO_RUST_CARGO_STACKSIZE=8192
# CONFIG_COVERAGE_TOOLCHAIN is not set
CONFIG_COVERAGE_NONE=y
" >> .config

make olddefconfig

Testing logs before change:

❯ make
Create version.h
Building Rust code with cargo...
error: "--target" takes a target architecture as an argument.

Run `rustup target list` to see possible targets.
make[3]: *** [Makefile:31: context] Error 101
make[2]: *** [Makefile:57: /Users/toku/nuttxspace/apps/examples/rust/hello_context] Error 2
make[1]: *** [Makefile:187: context] Error 2
make: *** [tools/Unix.mk:471: /Users/toku/nuttxspace/apps/.context] Error 2

Testing logs after change:

> make
...
  Compiling tokio v1.52.3
   Compiling hello v0.1.0 (/Users/toku/nuttxspace/apps/examples/rust/hello)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 20.92s
LN: platform/board to /Users/toku/nuttxspace/apps/platform/dummy
Register: gpio
Register: hello
Register: hello_rust_cargo
Register: dd
Register: dumpstack
Register: nsh
Register: sh
Register: ostest
CP:  /Users/toku/nuttxspace/nuttx/include/nuttx/config.h
CP:  /Users/toku/nuttxspace/nuttx/include/nuttx/fs/hostfs.h
LD:  nuttx
ld: warning: -ld_classic is deprecated and will be removed in a future release
ld: warning: -ld_classic is deprecated and will be removed in a future release

PR verification Self-Check

• My PR adheres to Contributing Guidelines and Documentation (git commit title and message, coding standard, etc).
• My PR is ready for review and can be safely merged into a codebase.

[lupyuen]

@no1wudi Could you review this PR? Thanks :-)